Leaching of lead and copper from flash smelting slag by citric acid

Abstract

As a direct-to-blister copper flash smelting slag contains important levels of copper (14%) and lead (2–4%) it is subjected to a process of high temperature reduction. To recover copper as well as lead the slag is subjected then to a process of decopperization by reducing the oxide metal compounds in an electric furnace. This study presents an alternative to the above process by recovering Pb and Cu from the slag by a hydrometallurgical route using citric acid solutions. The objective of this study was to determine process parameters at which the effectiveness of the lead leaching process is greatest with the minimum transfer of copper to the solution. This paper presents the results of laboratory tests on flash smelting slag leaching with citric acid solutions. Process parameters (time, temperature, citric acid concentration, l/s ratio) at which the Pb concentration decreases from the initial value (3.05%) to the value of 0.41–0.6% in the post-leaching sediment were determined. Analogous values for copper were 12.44% (before leaching) and 11.5–11.8% (after). The lead and copper content was determined by atomic absorption spectrometry (AAS). The hydrometallurgical method could successfully replace the existing treatment of slag in an electric furnace and converter.